Roles for primary cilia in gonadotrophin-releasing hormone neurones in the mouse

During embryonic development, gonadotrophin-releasing hormone (GnRH) neurones make an extraordinary migration out of the nose and into the brain where, in adulthood, they drive the pituitary regulation of gonadal function and fertility. Primary cilia are antennae-like, immotile organelles that project from the surface of nearly all cells, including GnRH neurones. Links between defects in primary cilia and a variety of human pathologies have been discovered that suggest a role for primary cilia in embryogenesis and reproductive function. The present study aimed to investigate whether GnRH neurone primary cilia are critical for their embryonic migration and the adult control of fertility. To achieve this, we used a Cre-loxP strategy to selectively disrupt primary cilia by deleting Kif3a, an intraflagellar transport protein family member essential for primary cilia assembly and function, specifically in GnRH neurones. Confocal analysis revealed that, in Kif3a(fl/fl) (WT-Kif3a) controls, all GnRH neurones possessed primary cilia, whereas, in GnRH-Cre(+/-) ;Kif3a(fl/fl) (GnRH-Kif3aKO) mice, 60% of GnRH neurones lacked any evidence of primary cilia and the remaining 40% possessed only stunted primary cilia (< 2 μm). Despite abolishing normal primary cilia assembly in GnRH neurones from embryogenesis, adult GnRH neurone distribution and reproductive function was remarkably normal. The total number of GnRH neurones was the same in GnRH-Kif3aKO and WT-Kif3a controls; however, a significant increase (25%) was identified in the number of GnRH neurones sampled through the midpoint of the rostral pre-optic area in GnRH-Kif3aKO mice (P < 0.05). The time to vaginal opening was not different in GnRH-Kif3aKO mice, although they displayed significantly advanced first oestrus (P < 0.05), and oestrous cycle length was increased (P < 0.05). However, females displayed normal basal levels of luteinising hormone, responded normally to oestrogen-induced negative- and positive-feedback, and displayed normal fecundity. Taken together, these data suggest that primary cilia and associated signal transduction pathways play a role in the topographical distribution and specific functions of GnRH neurones; however, they are not essential for fertility.

A cross-sectional analysis of the relationship between daily alcohol consumption and serum adiponectin levels among adults aged 40 years or more in a rural area of Korea

BACKGROUND/OBJECTIVES

Light-to-moderate alcohol consumption has been proposed to raise serum adiponectin levels, but this view is controversial. There is little information on the effect of heavy drinking. The aim of this study was to examine the relationship between alcohol consumption and serum adiponectin levels in healthy Koreans.

SUBJECTS/METHODS

The design of the study was cross-sectional, using data from the Korean Multi-Rural Communities Cohort Study (MRCohort), which is a part of the Korean Genome Epidemiology Study (KoGES). The subjects were 1542 individuals (635 men and 907 women) aged ≥ 40 years who were recruited in Yangpyeong-Gun, Kyunggi province, South Korea, in 2005 and 2006. Daily alcohol consumption was calculated from average frequency of alcohol consumption and the amount of alcohol consumed per occasion using a structured questionnaire and serum adiponectin levels were measured.

RESULTS

Although adiponectin levels appeared to be higher in those consuming moderate levels of alcohol than in nondrinkers, the difference was not statistically significant. Heavy drinking (≥ 90.0 g/day) was significantly related to reduced serum adiponectin levels (P=0.003), although the significance of the relationship was reduced after adjusting for potential confounders (P=0.061) such as age, waist/hip ratio, blood pressure, fasting blood glucose, current smoker, higher education, protein intake, vitamin C intake and vitamin E intake in men. The relation seemed to be stronger in individuals consuming alcohol in the form of takju (Korean rice wine; P=0.022).

CONCLUSIONS

Heavy alcohol drinking (≥ 90.0 g/day) may be related to lower serum adiponectin levels in Korean men.

TOPAS: an innovative proton Monte Carlo platform for research and clinical applications

PURPOSE

While Monte Carlo particle transport has proven useful in many areas (treatment head design, dose calculation, shielding design, and imaging studies) and has been particularly important for proton therapy (due to the conformal dose distributions and a finite beam range in the patient), the available general purpose Monte Carlo codes in proton therapy have been overly complex for most clinical medical physicists. The learning process has large costs not only in time but also in reliability. To address this issue, we developed an innovative proton Monte Carlo platform and tested the tool in a variety of proton therapy applications.

METHODS

Our approach was to take one of the already-established general purpose Monte Carlo codes and wrap and extend it to create a specialized user-friendly tool for proton therapy. The resulting tool, TOol for PArticle Simulation (TOPAS), should make Monte Carlo simulation more readily available for research and clinical physicists. TOPAS can model a passive scattering or scanning beam treatment head, model a patient geometry based on computed tomography (CT) images, score dose, fluence, etc., save and restart a phase space, provides advanced graphics, and is fully four-dimensional (4D) to handle variations in beam delivery and patient geometry during treatment. A custom-designed TOPAS parameter control system was placed at the heart of the code to meet requirements for ease of use, reliability, and repeatability without sacrificing flexibility.

RESULTS

We built and tested the TOPAS code. We have shown that the TOPAS parameter system provides easy yet flexible control over all key simulation areas such as geometry setup, particle source setup, scoring setup, etc. Through design consistency, we have insured that user experience gained in configuring one component, scorer or filter applies equally well to configuring any other component, scorer or filter. We have incorporated key lessons from safety management, proactively removing possible sources of user error such as line-ordering mistakes. We have modeled proton therapy treatment examples including the UCSF eye treatment head, the MGH stereotactic alignment in radiosurgery treatment head and the MGH gantry treatment heads in passive scattering and scanning modes, and we have demonstrated dose calculation based on patient-specific CT data. Initial validation results show agreement with measured data and demonstrate the capabilities of TOPAS in simulating beam delivery in 3D and 4D.

CONCLUSIONS

We have demonstrated TOPAS accuracy and usability in a variety of proton therapy setups. As we are preparing to make this tool freely available for researchers in medical physics, we anticipate widespread use of this tool in the growing proton therapy community.

Chemokine GPCR signaling inhibits β-catenin during zebrafish axis formation

We identify a novel mechanism of β-catenin inhibition involving, chemokine-GPCR signaling, which limits axis formation during zebrafish embryogenesis.

Embryonic axis formation in vertebrates is initiated by the establishment of the dorsal Nieuwkoop blastula organizer, marked by the nuclear accumulation of maternal β-catenin, a transcriptional effector of canonical Wnt signaling. Known regulators of axis specification include the canonical Wnt pathway components that positively or negatively affect β-catenin. An involvement of G-protein coupled receptors (GPCRs) was hypothesized from experiments implicating G proteins and intracellular calcium in axis formation, but such GPCRs have not been identified. Mobilization of intracellular Ca²⁺ stores generates Ca²⁺ transients in the superficial blastomeres of zebrafish blastulae when the nuclear accumulation of maternal β-catenin marks the formation of the Nieuwkoop organizer. Moreover, intracellular Ca²⁺ downstream of non-canonical Wnt ligands was proposed to inhibit β-catenin and axis formation, but mechanisms remain unclear. Here we report a novel function of Ccr7 GPCR and its chemokine ligand Ccl19.1, previously implicated in chemotaxis and other responses of dendritic cells in mammals, as negative regulators of β-catenin and axis formation in zebrafish. We show that interference with the maternally and ubiquitously expressed zebrafish Ccr7 or Ccl19.1 expands the blastula organizer and the dorsoanterior tissues at the expense of the ventroposterior ones. Conversely, Ccr7 or Ccl19.1 overexpression limits axis formation. Epistatic analyses demonstrate that Ccr7 acts downstream of Ccl19.1 ligand and upstream of β-catenin transcriptional targets. Moreover, Ccl19/Ccr7 signaling reduces the level and nuclear accumulation of maternal β-catenin and its axis-inducing activity and can also inhibit the Gsk3β -insensitive form of β-catenin. Mutational and pharmacologic experiments reveal that Ccr7 functions during axis formation as a GPCR to inhibit β-catenin, likely by promoting Ca²⁺ transients throughout the blastula. Our study delineates a novel negative, Gsk3β-independent control mechanism of β-catenin and implicates Ccr7 as a long-hypothesized GPCR regulating vertebrate axis formation.

The arrangement of dorsoventral (back to belly) and anteroposterior (head to tail) embryonic structures is specified early during animal embryogenesis. In vertebrates, this process of axes formation is initiated by β-catenin, a transcriptional effector of Wnt signaling, which marks the prospective dorsal side. Thus far, all known regulators of axis specification that affect β-catenin include components of the Wnt pathway. G protein-coupled receptors (GPCRs), as well as Ca²⁺ signaling, have also been hypothesized to inhibit β-catenin and axis formation, however the identity of such GPCRs has remained unclear. Here, we identify two novel regulators of axis formation: the zebrafish Ccr7 chemokine GPCR and one of its ligands, Ccl19.1, both of which are uniformly expressed in the early zebrafish embryo. We show that reducing the expression of Ccr7 or Ccl19.1 increases β-catenin levels and also the dorsoanterior tissues at the expense of the ventroposterior ones. Conversely, an excess of Ccr7 or Ccl19.1 lowers β-catenin levels and limits axis formation. Further experiments show that Ccr7 acts upstream of β-catenin transcriptional targets. Our study delineates a novel mechanism for the negative control of β-catenin, whereby Ccr7 increases β-catenin degradation in a Gsk3b-independent manner, likely by promoting Ca²⁺ signaling throughout the embryo. In a new model of axis specification we propose that Ccr7 acts as a long-hypothesized GPCR that provides a global inhibition of β-catenin to ensure the precise formation of embryonic axes.

The fate of Treponema denticola within human gingival epithelial cells

Treponema denticola is one of the major pathogens associated with chronic periodontitis. Bacterial invasion into gingival tissues is a critical process in the pathogenesis of periodontal disease. We recently reported that T. denticola can invade gingival epithelial cells. The aim of this study is to determine the fate of internalized T. denticola in gingival epithelial cells. Immortalized human gingival epithelial HOK-16B cells were infected with 5- (and 6-) carboxy-fluorescein diacetate succinimidyl ester (CFSE)-labeled live or heat-killed T. denticola for 24 h, and the presence of bacteria inside the cells was confirmed by confocal microscopy. Live T. denticola, but not heat-killed bacteria, invaded HOK-16B cells. Confocal microscopy also revealed that internalized T. denticola rarely colocalized with either endosomes or lysosomes. Transmission electron microscopy of infected cells showed that intracellular T. denticola was localized inside endosome-like structures. Although a culture-based antibiotics protection assay could not detect viable intracellular T. denticola 12 h after infection, a substantial number of bacteria were observed by confocal microscopy and weak expression of bacterial 16S ribosomal RNA was detected 48 h after infection. In addition, flow cytometric analysis of HOK-16B cells infected with CFSE-labeled T. denticola showed no loss of fluorescence over 48 h. Collectively, T. denticola invades gingival epithelial cells and remains within the host cells for many hours by resisting endolysosomal degradation. These findings may provide new insight into the role of T. denticola in the pathogenesis of periodontitis.